Magnetic storage media, which include magnetic tape and magnetic disks, are commonly used for storage and retrieval of data. The data is typically encoded in magnetizations on the recording surface of the magnetic media. A typical magnetic recording medium includes a thin layer of ferromagnetic material, such as gamma ferric oxide, supported by a non-magnetic substrate. The ferromagnetic material is a material that can be permanently magnetized by the application of an external magnetic field. The ferromagnetic material typically includes magnetic particles mixed with a binder material that can attach to the non-magnetic substrate. The ferromagnetic material is typically applied to the non-magnetic substrate in a coating process. Alternatively, metal evaporation techniques or sputtering techniques can be used to apply the ferromagnetic material on the non-magnetic substrate.
Magneto-optic read techniques have been developed for readout of data stored on magnetic media. Magneto-optic read techniques take advantage of both electromagnetic principles and optics to facilitate data readout. A magneto-optic head can capture fringing magnetic fields produced by the magnetic particles that are encoded with data on the surface of the magnetic media. Polarized light is reflected off the read head, and detected by a light detector such as a linear charged coupled device (CCD). When the light is reflected, a polarization rotation occurs, sometimes referred to as the longitudinal Kerr effect. The polarization rotation is proportional to the magnetization in the read head. Thus, the polarization rotation of the detected light can be interpreted to facilitate readout of the data magnetically encoded in the surface of the magnetic media.
Magneto-optic heads include a ferromagnetic layer that captures fringing magnetic fields produced by magnetic media. Typically, these ferromagnetic layers are unpatterned and include a plurality of magnetic domains, i.e., different regions of the layers in which the magnetic fields of the atoms of the ferromagnetic material are aligned. The location, boundaries, and alignment of magnetic domains within ferromagnetic layers of unconstrained magneto-optic heads are generally random, e.g., the ferromagnetic layers tend to reside in a random multi-domain state. When magnetized by the fringing magnetic fields produced by a magnetic medium, such ferromagnetic layers will respond in a non-uniform manner that depends upon the domain configuration of the portion of the layer that is being magnetized. Such non-uniform cross-medium response impairs the ability of unconstrained magneto-optic heads to accurately read adjacent tracks across a medium.